Gravel pack systems allow many downhole procedures to take place in a single trip. A gravel pack assembly typically contains sections of screen that extend from a packer. An inner string that includes a crossover tool is movable with respect to the set packer for selective sealing relation with a polished bore in the packer. In this manner fluids can be circulated when the assembly is run in and gravel can be deposited outside the screens while return fluids can come up through the screens and up a wash pipe. These return fluids can then pass through a valve in an uphole direction and go through the crossover and back to the surface through the annulus above the set packer. Alternatively, the crossover can allow the gravel to be deposited with fluid squeezed into the formation in a procedure called a frac pack. The crossover is simply positioned with respect to the packers and seal bores in a manner where no return port through the wash pipe and back to the surface is open.
Regardless of whether the gravel is deposited with fluid returns to the surface or whether the fluid is forced into the formation when the gravel is deposited outside the screens, the excess gravel in the string leading down to the crossover has to be removed, typically by a process called reversing out. In this step the crossover is repositioned so that fluid pumped from the surface in the annular space above the packer is allowed into the tubing above the packer so that the excess gravel can be brought to the surface. It is the locating of these positions downhole that is vital to the correct operation of the tool. Performing this procedure can build pressure near the crossover and a risk of fluid loss to the formation with this built up pressure is a possibility. Fluid loss to the formation can diminish its productivity and excessive fluid loss to the formation may inhibit or prevent reverse circulating of the excess gravel from the workstring. For these reasons a fluid loss control valve in the wash pipe extending into a packer seal bore from the crossover has been used. These fluid loss control valves are illustrated in patents relating to gravel packing operations such as U.S. Pat. Nos. 7,290,610; 7,128,151; 7,032,666 and 6,983,795.
As an introduction to an understanding of the preferred embodiment, a brief discussion of the prior designs and the issues it presented will be undertaken in a summary form. FIG. 1 shows a common prior art assembly for gravel packing. A wellbore 20 has a string 22 with a packer 24 shown in a set position. A crossover tool 26 with a wash pipe 28 extends through a screen assembly 30 that is properly located by a formation 31 using a tubular spacer 29. The screen assembly 30 has profiles 32 on which a collet 34 that is connected to the wash pipe 28 can be landed to provide the desired flow configurations for the gravel packing operation. In order to direct fluid flow it is necessary that the packer 24 sealing bore 38′ be compatible with the crossover tool 26, such that the crossover tool seals in the seal bore. In the FIG. 1 position a fluid loss control valve 36 is locked in the open position. The FIG. 1 position allows circulation with flow coming down the string 22 and going through the crossover tool 26 to emerge outside the screen assembly 30. Flow then goes through the screen assembly 30 and into the wash pipe 28 and through the flow control valve 36 and back through the crossover tool 26 to the annulus above packer 24 and around the string 22 to the surface.
Note that in FIG. 1 the collet 34 is set down on one of the profiles 32 to define a circulating position. In FIG. 2 the collet 34 is back to the same position as in FIG. 1 to define a position for delivering gravel 27 either by circulation or by what's called a frac pack where the returns in the annulus 44 above the packer 24 are shut off at the surface. After that, further string manipulation in FIGS. 3 and 4 allows the collet 34 to indicate in different locations and directions on profiles 32 so as to place the internal assembly in position to evacuate excess gravel from the crossover tool 26 in FIG. 3 and from the string above the packer 24 in FIG. 4.
With this prior art configuration and the crossover tool 26 sealing in the packer 24 sealing bore 38′ it was necessary to have the profiles 32 smaller than the packer 24 sealing bore 38′. As a result when the well is put on production, the profiles present resistance to production flow through the screen assembly 30.
The present invention is directed at finding an alternative location for these profiles and the preferred location is in a region above the packer where the profiles can be larger since the annulus above the packer need not be as large as below it since only screened returns pass through that annulus. These and other aspects of the present invention will become more apparent from a review of the description of the preferred embodiment and the associated drawing while recognizing that the appended claims define the literal and equivalent scope of the invention.